Abstract:

An object of the present invention is to provide a solar cell module in
which a solar cell element connected with a substrate by wire bonding is
sealed and which is capable of preventing deformation of a bonding wire.
For this object, the solar cell module of the present invention is
designed such that the bonding wire is sealed with potting resin so that
a surface of the solar cell element, which surface is opposite to the
substrate, is exposed.

Claims:

1. A solar cell module, including a substrate and a solar cell element
connected with the substrate by wire,the wire being sealed with high
viscosity resin so that a surface of the solar cell element, which
surface is opposite to the substrate, is exposed.

2. The solar cell module as set forth in claim 1, the solar cell module
being obtained by coating the high viscosity resin and the solar cell
element with a first sheet made of a transparent adhesive.

3. The solar cell module as set forth in claim 2, the solar cell module
being obtained by coating the first sheet with a second sheet which is
transparent and has predetermined heat-resistance.

4. The solar cell module as set forth in claim 1, wherein when a
temperature of the high viscosity resin is 25.degree. C., the high
viscosity resin has viscosity ranging from 5 to 500 Pas.

5. The solar cell module as set forth in claim 1, wherein the high
viscosity resin is transparent.

6. The solar cell module as set forth in claim 2, wherein the first sheet
is made of ethylene vinyl acetate.

7. A method for producing a solar cell module including a substrate and a
solar cell element connected with the substrate by wire,the method
comprising the steps of:sealing the wire with high viscosity resin so
that a surface of the solar cell element, which surface is opposite to
the substrate, is exposed, andcoating the high viscosity resin and the
solar cell element with a first sheet made of a transparent adhesive.

8. The method as set forth in claim 7, further comprising the steps
of:coating the first sheet with a second sheet which is transparent and
has predetermined heat-resistance, andthermocompressing the second sheet
against the substrate.

9. A method for producing a solar cell module including a substrate and a
solar cell element connected with the substrate by wire,the method
comprising the steps of:coating the solar cell element with a first sheet
made of a transparent adhesive, the first sheet having a thickness larger
than a height of the wire as seen from the substrate, and the first sheet
lacking a portion to coat the wire; andcoating the first sheet with a
second sheet which is transparent and has heat-resistance.

10. The method as set forth in claim 9, further comprising the step of
thermocompressing the second sheet against the substrate.

[0002]The present invention relates to a solar cell module produced by
sealing a solar cell element connected with (mounted on) a substrate by
wire bonding, and to a method for producing the solar cell module.

BACKGROUND ART

[0003]A conventional technique for sealing a solar cell element connected
with (mounted on) a substrate by wire bonding is a technique for coating
the solar cell element with epoxy resin by use of a mold and sealing the
solar cell element.

[0004]However, since the conventional technique requires a mold, it is
difficult to carry out the technique at low costs. Further, since it is
impossible to seal a plurality of solar cell elements together by the
technique, the technique is inappropriate for mass production of solar
cell modules. Further, in the technique, epoxy resin is poured into a
mold and then the epoxy resin is taken out of the mold by use of curing
and contraction of the epoxy resin at the time of molding, but the
technique suffers from a problem of flexion of the completed solar cell
module after the epoxy resin is taken out of the mold. Further, in the
technique of molding epoxy resin, the molding must be carried out while
the mold is heated up to a high temperature of approximately
145-160° C. This causes a so-called bimetal phenomenon due to a
difference in linear expansion coefficient between epoxy resin and a
substrate, and when the solar cell module as a whole is cooled down to a
normal temperature, the solar cell module gets flexed.

[0005]In order to deal with these problems, as the technique for sealing a
solar cell element connected with a substrate by wire bonding, attention
is paid to a technique for coating a solar cell element with a
transparent adhesive sheet called an EVA (Ethylene Vinyl Acetate) sheet
and laminate-sealing the solar cell element.

[0006]In general, the EVA sheet is used as a member for sealing a solar
cell element in a solar cell module for housing. Since the technique
using the EVA sheet does not require a mold, the technique can be carried
out at low costs. Further, in the technique, a plurality of solar cell
elements are coated with one EVA sheet with a large area and sealed
together, and therefore the technique is suitable for, mass production.
Further, since the technique using the EVA sheet does not require a mold,
the technique prevents the problem of flexion of a completed solar cell
module in the technique using a mold.

[0009]In the technique using the EVA sheet, a solar cell element 212 is
connected with a substrate 213 via a bonding wire 211, and then the
bonding wire 211 and the solar cell element 212 are coated with an EVA
sheet 214, and the EVA sheet 214 is heated up to approximately
130° C. and fused while pressed, and the bonding wire 211 and the
solar cell element 212 are laminate-sealed by ethylene vinyl acetate.
Thus, a solar cell module 210 is produced as a commercial product. In the
technique using the EVA sheet 214, when the bonding wire 211 and the
solar cell element 212 are coated with the EVA sheet 214, a load derived
from the weight of the EVA sheet 214 is applied to the bonding wire 211,
and the load causes deformation of the bonding wire 211 (see FIG. 11).
Deformation of a boding wire (wire) is hereinafter referred to as "wire
sweep".

[0010]The present invention was made in view of the foregoing problems. An
object of the present invention is to provide a solar cell module which
seals a solar cell element connected with a substrate by wire bonding and
which is capable of preventing the wire sweep.

Solution to Problem

[0011]In order to solve the foregoing problems, a solar cell module of the
present invention is a solar cell module, including a substrate and a
solar cell element connected with the substrate by wire, the wire being
sealed with high viscosity resin so that a surface of the solar cell
element, which surface is opposite to the substrate, is exposed.

[0012]With the arrangement, since the wire is sealed with resin, the wire
is fixed (reinforced) by the resin. This reduces the possibility of the
wire sweep due to a load applied to the wire. Therefore, the arrangement
allows preventing the wire sweep.

[0013]Although not in the field of a solar cell module, Patent Literature
1 discloses a semiconductor device in which at least a connection between
a pad of a semiconductor chip and a bonding wire is coated with
reinforcing resin in order to prevent the wire sweep. In the
semiconductor device disclosed in Patent Literature 1, resin merely made
in a liquid form by heating epoxy resin is dropped onto the connection
etc. to form the reinforcing resin. Such reinforcing resin wets and
spreads over a surface of a semiconductor chip of a semiconductor device,
in particular, an entire surface of the semiconductor chip opposite to a
substrate. In fact, in any of the semiconductor devices disclosed in
Patent Literature 1, the reinforcing resin wets and spreads over the
entire surface.

[0014]If the reinforcing resin in Patent Literature 1 is applied to a
solar cell module in which a solar cell element is connected with a
substrate by wire, the reinforcing resin covers an entire surface of the
solar cell element opposite to a substrate, and consequently light
incident to the solar cell element is blocked by the reinforcing resin.
This causes a possibility that the solar cell element, and therefore the
solar cell module, has greatly reduced efficiency in power generation, or
in a worst case, power generation gets impossible.

[0015]In order to deal with this problem, the solar cell module of the
present invention employs high viscosity resin as resin for sealing and
fixing a wire. When the high viscosity resin seals and fixes the wire,
the high viscosity resin does not wet and spared over a surface of the
solar cell element opposite to a substrate. This provides on the surface
an exposed part which is not covered with the high viscosity resin, and
therefore light incident to the solar cell element is not blocked.
Consequently, the solar cell module of the present invention allows
preventing the wire sweep without resulting in great dropping in the
efficiency in power generation or in impossibility of power generation.

[0016]Therefore, since the solar cell module of the present invention is
designed such that the wire is sealed by the high viscosity resin in
order to expose the surface of the solar cell element opposite to the
substrate, the solar cell module of the present invention is favorable
for preventing the problem of wire sweep appearing in a solar cell module
in which a solar cell element connected with a substrate by wire bonding
is sealed.

[0017]In order to solve the foregoing problems, a method of the present
invention for producing a solar cell module is a method for producing a
solar cell module including a substrate and a solar cell element
connected with the substrate by wire, the method comprising the steps of:
sealing the wire with high viscosity resin so that a surface of the solar
cell element, which surface is opposite to the substrate, is exposed, and
coating the high viscosity resin and the solar cell element with a first
sheet made of a transparent adhesive.

[0018]In the conventional art, a mold for coating by epoxy resin for
sealing high viscosity resin and a solar cell element has been required.
However, with the arrangement of the present invention, such mold is
unnecessary. This allows production at low costs, and allows providing a
solar cell module at a low price. Further, with the arrangement, a
plurality of solar cell elements are coated with one first sheet with a
large area and laminate-sealed together, and consequently a plurality of
solar cell modules can be produced together. Thus, a solar cell module
appropriate for mass production can be realized. In particular, use of an
EVA sheet made of inexpensive ethylene vinyl acetate as the first sheet
results in great reduction in the costs and the price of a solar cell
module. When the solar cell module is coated with the first sheet, a load
derived from the weight of the first sheet is applied to a wire. However,
with the arrangement of the present invention, since the wire is fixed by
high viscosity resin, it is possible to prevent the wire sweep.

[0019]In order to solve the foregoing problems, a method of the present
invention for producing a solar cell module is a method for producing a
solar cell module including a substrate and a solar cell element
connected with the substrate by wire, the method comprising the steps of:
coating the solar cell element with a first sheet made of a transparent
adhesive, the first sheet having a thickness larger than a height of the
wire as seen from the substrate, and the first sheet lacking a portion to
coat the wire; and coating the first sheet with a second sheet which is
transparent and has heat-resistance.

[0020]With the arrangement, since the first sheet lacks the portion to
coat the wire, a load applied to the wire, which load is derived from the
weight of the first sheet, can be reduced or eliminated. Consequently,
the solar cell module of the present invention allows preventing the wire
sweep even when the high viscosity resin is not used.

[0021]Further, with the arrangement, since the high viscosity resin is not
used, it is possible to further downsize a part that may prevent light
from being incident to the solar cell element. This allows further
increasing the efficiency in power generation of the solar cell element.

[0022]It should be noted that in a case where the thickness of the first
sheet is smaller than the height of the wire as seen from the substrate,
when the first sheet coats the solar cell element, the wire protrudes
above the first sheet. When the wire protrudes above the first sheet,
coating the first sheet with the second sheet may cause the wire sweep
because of a load applied to the wire which is derived from the weight of
the second sheet. In order to prevent a load derived from the weight of
the second sheet from being applied to the wire, it is necessary for the
first sheet to have a thickness larger than the height of the wire as
seen from the substrate.

ADVANTAGEOUS EFFECTS OF INVENTION

[0023]As described above, the solar cell module of the present invention
is a solar cell module, including a substrate and a solar cell element
connected with the substrate by wire, the wire being sealed with high
viscosity resin so that a surface of the solar cell element, which
surface is opposite to the substrate, is exposed.

[0024]Further, the method of the present invention for producing a solar
cell module is a method for producing a solar cell module including a
substrate and a solar cell element connected with the substrate by wire,
the method comprising the steps of: sealing the wire with high viscosity
resin so that a surface of the solar cell element, which surface is
opposite to the substrate, is exposed, and coating the high viscosity
resin and the solar cell element with a first sheet made of a transparent
adhesive.

[0025]Further, the method of the present invention for producing a solar
cell module is a method for producing a solar cell module including a
substrate and a solar cell element connected with the substrate by wire,
the method comprising the steps of: coating the solar cell element with a
first sheet made of a transparent adhesive, the first sheet having a
thickness larger than a height of the wire as seen from the substrate,
and the first sheet lacking a portion to coat the wire; and coating the
first sheet with a second sheet which is transparent and has
heat-resistance.

[0026]Consequently, in the solar cell module in which the solar cell
element connected with the substrate by wire bonding is sealed, it is
possible to prevent the wire sweep.

BRIEF DESCRIPTION OF DRAWINGS

[0027]FIG. 1 is a cross sectional drawing showing a configuration of a
solar cell module in accordance with one embodiment of the present
invention. FIG. 1 also serves as a cross sectional drawing showing how to
produce a solar cell module shown in FIG. 5, and showing the step of
sealing a bonding wire with potting resin.

[0028]FIG. 2 is a cross sectional drawing showing how to produce the solar
cell module shown in FIGS. 5 and 6, and showing the step of connecting a
solar cell element with a substrate by wire bonding.

[0029]FIG. 3 is a cross sectional drawing showing how to produce the solar
cell module shown in FIG. 5, and showing the step of coating the solar
cell module shown in FIG. 1 with an EVA sheet and a PET sheet.

[0030]FIG. 4 is a cross sectional drawing showing how to produce the solar
cell module shown in FIG. 5, and showing the step of thermocompressing
the PET sheet shown in FIG. 3 against the substrate.

[0031]FIG. 5 is a cross sectional drawing showing a configuration of a
solar cell module of the present invention which is completed as a
commercial product.

[0032]FIG. 6 is a cross sectional drawing showing another configuration of
a solar cell module of the present invention which is completed as a
commercial product.

[0033]FIG. 7 is a perspective drawing showing a substrate connected with a
solar cell element via a bonding wire, an EVA sheet, and a PET sheet in
the solar cell module shown in FIG. 6.

[0034]FIG. 8 is a perspective drawing showing how to produce the solar
cell module shown in FIG. 6, and showing the step of coating with the EVA
sheet the FIG. 7 substrate connected with the solar cell element via the
bonding wire.

[0035]FIG. 9 is a perspective drawing showing how to produce the solar
cell module shown in FIG. 6 and showing the step of coating the EVA sheet
in FIG. 8 with the PET sheet.

[0036]FIG. 10 is a perspective drawing showing how to produce the solar
cell module shown in FIG. 6 and showing the step of thermocompressing the
PET sheet in FIG. 9 against the substrate.

[0037]FIG. 11 is a cross sectional drawing showing a configuration of a
conventional solar cell module.

DESCRIPTION OF EMBODIMENTS

[0038]FIG. 1 is a cross sectional drawing showing a configuration of a
solar cell module in accordance with one embodiment of the present
invention.

[0040]The bonding wire 1 is a metal wire via which the solar cell element
2 is connected with the substrate 3 by well known wire bonding. One end
of the bonding wire 1 is connected with the solar cell element 2 via a
surface electrode 21 and the other end, of the bonding wire 1 is
connected with an electrode (not shown) of the substrate 3. Thus, the
solar cell element 2 is mounted on the substrate 3 via the bonding wire
1, and the solar cell element 2 and the substrate 3 are electrically
connected with each other via the bonding wire 1. Examples of a material
for the bonding wire 1 include gold, copper, and aluminum.

[0041]The solar cell element 2 is a semiconductor element that receives
light such as a solar ray and converts light energy obtained from the
light into electric energy by photoelectric transfer, allowing power
generation in response to incident light (so-called photovoltaic
generation). This element may be also referred to as a solar cell or
merely a cell. Specifically, in the solar cell element 2, electrons (not
shown) receive light energy, and convert the light energy into electric
energy by a photovoltaic effect. An example of the solar cell element 2
is a silicon semiconductor such as a monocrystalline silicon and a
polycrystalline silicon. Alternatively, a well known solar cell element
may be used.

[0042]The substrate 3 is a substrate on which the solar cell element 2 is
mounted. Examples of the substrate 3 include a glass substrate, a glass
epoxy substrate, a polyimide substrate, and a polyvinyl substrate. The
thickness of the substrate 3 is not particularly limited. However,
considering that the substrate 3 requires a predetermined strength and
weight, the thickness should range from approximately 0.1 to 30 mm in a
case of a glass substrate. The substrate 3 may be made of plural
materials, and may be covered with a metal film, a transparent conductive
film, or an insulating film on its surface. It should be noted that since
the substrate 3 is subjected to direct thermocompression by pressing a
heater 7 (see FIG. 4) against the substrate 3 in the step of producing a
solar cell module 150 (see FIG. 5) as a commercial product, it is
desirable that the substrate 3 has a heat-resistance to some extent, e.g.
a heat-resistance up to approximately 200° C.

[0043]Although not shown in the drawing, a backside electrode is further
provided between the solar cell element 2 and the substrate 3, and the
solar cell element 2 and the substrate 3 are electrically connected with
each other via the backside electrode.

[0044]The potting resin 5 is resin preferably used for potting. An example
of the potting resin 5 is epoxy resin. The potting resin 5 coats the
bonding wire 1 in such a manner that the potting resin 5 covers
substantially all of the bonding wire 1, thereby selectively sealing at
least the bonding wire 1. That is, the potting resin 5 partially seals
the solar cell module 100 by sealing substantially all of the bonding
wire 1. The sealing of the bonding wire 1 by the potting resin 5 fixes
(reinforces) the bonding wire 1. Since the bonding wire 1 is fixed by the
potting resin 5, it is possible to reduce the possibility that the load
applied to the bonding wire 1 causes the wire sweep. Therefore, with the
above arrangement, it is possible to prevent the wire sweep of the
bonding wire 1.

[0045]The potting resin 5 used here is so-called high viscosity resin
whose viscosity ranges, for example, from 5 to 500 Pas when the
temperature of the resin is 25° C. The following explains why the
high viscosity resin is used as the potting resin 5.

[0046]If the potting resin 5 in the solar cell module 100 is so-called low
viscosity resin whose viscosity is less than 5 Pas (when the temperature
of the resin is 25° C.), the potting resin 5 wets and spreads over
the whole of a surface 22 that is a surface of the solar cell element 2
opposite to the substrate 3 (a surface of the solar cell element 2 which
is positioned upward in FIG. 1), covering the whole of the surface 22.
Consequently, light incident to the solar cell element 2 is blocked by
the potting resin 5, resulting in great reduction in light energy
supplied to the solar cell element 2. In a worst case, the solar cell
element 2 cannot receive light energy at all. Consequently, in the solar
cell element 2, and therefore in the solar cell module 100, efficiency in
power generation drops greatly, or in a worst case, power generation gets
impossible.

[0047]An example of a technique for preventing the potting resin 5 from
wetting and spreading over the whole of the surface 22 while low
viscosity resin is used as the potting resin 5 in the solar cell module
100 is a technique for forming a protrusion (protrusive electrode; not
shown) made of silver paste for example on the surface 22 in order to
prevent flow of the potting resin 5. However, when the technique is used,
the formed protrusion covers the surface 22, and the protrusion blocks
light incident to the solar cell element 2. Consequently, light energy
supplied to the solar cell element 2 drops greatly (efficiency in power
generation drops greatly), and in a worst case, the solar cell element 2
cannot receive light energy (cannot generate power).

[0048]On the other hand, if the potting resin 5 in the solar cell module
100 is high viscosity resin, the potting resin 5 does not wet and spread
over the whole of the surface 22, depending on the degree of viscosity of
the high viscosity resin. Consequently, the potting resin 5 with high
viscosity is advantageous in that it can be selectively provided on a
desired part of the surface 22. In the solar cell module 100, with use of
the advantage of the potting resin 5 with high viscosity, the potting
resin 5 is provided in such a manner as to selectively seal the bonding
wire 1. This allows the whole of the surface 22 to have a sufficiently
broad exposed area that is not covered with the potting resin 5. This
prevents blocking of light incident to the solar cell element 2.
Consequently, in the solar cell module 100, it is possible to prevent the
wire sweep of the bonding wire 1 without resulting in great drop in the
efficiency in power generation or in total impossibility of power
generation.

[0049]Therefore, since the solar cell module 100 is designed such that the
bonding wire 1 is sealed by the potting resin 5 with high viscosity in
order to expose the surface 22 of the solar cell element 2 opposite to
the substrate 3, the solar cell module 100 is favorable for preventing
the problem of wire sweep appearing in a solar cell module in which a
solar cell element connected with a substrate by wire bonding is sealed.

[0050]Further, as detailed later, the potting resin 5 with high viscosity
has a function of preventing an excessive pressure from being applied to
the solar cell module when the solar cell module is subjected to
thermocompression in the step of producing a solar cell module 150 (see
FIG. 5), and a function of protecting the bonding wire 1 from a pressure
which is caused depending on a thermal cycle of the solar cell module.

[0051]As shown in FIG. 1, the potting resin 5 may further seal the
vicinity of the bonding wire 1. This allows further solidly fixing the
bonding wire 1. However, it should be noted that in a case where the
potting resin 5 further seals the vicinity of the bonding wire 1 and thus
covers the surface 22 of the solar cell element 2, if the potting resin 5
covers a larger part of the surface 22, light incident to the solar cell
element 2 is more blocked by the potting resin 5, resulting in drop of
the efficiency in power generation. As long as the above is noted, what
part is covered by the potting resin 5 is not particularly limited,
provided that the potting resin 5 covers substantially the whole of the
bonding wire 1.

[0052]It is favorable that the potting resin 5 is designed such that the
potting resin 5 has a viscosity ranging from 5 to 500 Pas when the
temperature thereof is 25° C.

[0053]If the potting resin 5 is designed such that the potting resin 5 has
a viscosity of less than 5 Pas when the temperature thereof is 25°
C., the potting resin 5 wets and spreads over the solar cell element 2
and thus covers the whole of the surface 22 of the solar cell element 2
which surface 22 is opposite to the substrate 3. Consequently, light
incident to the solar cell element 2 is blocked by the potting resin 5.
As a result, in the solar cell module 100, light energy supplied to the
solar cell element 2 drops greatly, or in a worst case, the solar cell
element 2 cannot receive light energy. Consequently, in the solar cell
element 2, and therefore in the solar cell module 100, the efficiency in
power generation drops greatly, or in a worst case, power generation gets
impossible. Further, when the bonding wire 1 is sealed by the potting
resin 5 having a viscosity of less than 5 Pas, the bonding wire 1 is
fixed less solidly by the potting resin 5 and the bonding wire 1 cannot
have a sufficient strength against the load, resulting in a possibility
of the wire sweep of the bonding wire 1.

[0054]In contrast thereto, if the potting resin 5 is designed such that
the potting resin 5 has a viscosity of more than 500 Pas when the
temperature thereof is 25° C., the potting resin 5 is very
difficult to wet and spread, which makes insufficient filling of the
potting resin 5 into gaps between the solar cell element 2 and the
bonding wire 1, and the insufficient filling may cause spaces. This may
result in decrease in the quality and reliability of the solar cell
module 150 (see FIG. 5).

[0055]In view of the above, the potting resin 5 is preferably designed
such that the potting resin 5 has a viscosity ranging from 5 to 500 Pas
when the temperature thereof is 25° C.

[0056]Further, the potting resin 5 is preferably transparent high
viscosity resin. When the potting resin 5 is transparent, light is
incident to the solar cell element 2 via the potting resin 5. This allows
preventing the blocking of light incident to the solar cell element 2 by
the potting resin 5.

[0057]When the potting resin 5 is transparent, the solar cell element 2
can generate power also at a part covered with the potting resin 5.
Accordingly, in this case, an exposed part of the surface 22 may be
small, or the exposed part of the surface 22 do not have to exist at all.
In this case, the solar cell module 100 may be designed such that the
exposed surface 22 of the solar cell element 2 is covered with the
transparent potting resin 5. This broadens a portion sealed by the
potting resin 5, allowing the potting resin 5 to further solidly fix the
bonding wire 1, further effectively preventing the wire sweep. In this
case, since it is unnecessary to secure an exposed part of the surface
22, the potting resin 5 do not necessarily have to be high viscosity
resin.

[0058]As a method for producing a solar cell module in accordance with one
embodiment of the present invention, the following explains steps of
producing the solar cell module 150 (see FIG. 5) from the solar cell
module 100 shown in FIG. 1, with reference to FIGS. 2-5.

[0059]Initially, in the step shown in FIG. 2, the solar cell element 2 is
connected with the substrate 3 by well known wire bonding using the
bonding wire 1. That is, in the step shown in FIG. 2, as a preparation
for producing the solar cell module 100 shown in FIG. 1, one end of the
bonding wire 1 is connected with the solar cell element 2 via the surface
electrode 21, and the other end of the bonding wire 1 is connected with
an electrode (not shown) of the substrate 3.

[0060]Then, the bonding wire 1 is covered with the potting resin 5 by well
known potting, and is sealed by the potting resin 5. Thus, the surface 22
of the solar cell element 2 is exposed to produce the solar cell module
100 (see FIG. 1).

[0061]Then, in the step shown in FIG. 3, the solar cell element 2 and the
potting resin 5 sealing the bonding wire 1 in the solar cell module 100
are coated with the EVA sheet (first sheet) 4.

[0062]When the solar cell element 2 and the potting resin 5 sealing the
bonding wire 1 are laminate-sealed by the EVA sheet 4, it is unnecessary
to use a mold for coating epoxy resin which is required in sealing in the
conventional art. This allows production at low costs, allowing the solar
cell module 150 (see FIG. 5) to be sold at a low price. Further, in this
case, it is possible to produce a plurality of solar cell modules 150
together by coating not only the solar cell element 2 but also other
solar cell elements (not shown in the drawing) with one EVA sheet 4 and
laminate-sealing them together. Therefore, this method is favorable for
mass production. In particular, when the EVA sheet 4 made of inexpensive
ethylene vinyl acetate is used in laminate-sealing, it is possible to
greatly reduce costs and therefore reduce the price of the solar cell
module 150. Further, since the EVA sheet 4 has lower elasticity,
extremely higher flexibility, and lower laminate temperature (mentioned
later) than epoxy resin used in the sealing in the conventional art using
a mold, it is possible to realize the solar cell module 150 with
extremely small flexion.

[0063]When the solar cell module 100 (see FIG. 1) is coated with the EVA
sheet 4, a load derived from the weight of the EVA sheet 4 is applied to
the bonding wire 1. However, since the bonding wire 1 is fixed by the
potting resin 5, it is possible to prevent the wire sweep of the bonding
wire 1.

[0064]The EVA sheet 4 has low elasticity and extremely high flexibility.
Consequently, when the solar cell module 150 (see FIG. 5) is subjected to
a thermal cycle of repeating cooling down to approximately -30° C.
and heating up to approximately 100° C., the EVA sheet 4 is
stretched greatly. When the EVA sheet 4 is stretched greatly, an
unexpectedly great pressure is applied to the bonding wire 1, which may
break the bonding wire 1. However, since the bonding wire 1 is sealed and
fixed by the potting resin 5, it is possible to prevent the breakage of
the bonding wire 1. That is, the sealing of the bonding wire 1 by the
potting resin 5 protects the bonding wire 1 in the thermal cycle. In
particular, when the potting resin 5 has low linear expansion coefficient
and high elasticity, the potting resin 5 can further effectively protect
the bonding wire 1 in the thermal cycle.

[0065]The EVA sheet 4 may be replaced with a transparent adhesive sheet
made of a material such as PBT (Polybutylene terephthalate), an acrylic
material, and a silicone material.

[0066]Further, in the step shown in FIG. 3, the EVA sheet 4 is coated with
a PET sheet (second sheet) 6 made of PET (Polyethylene Terephthalate).

[0067]The PET sheet 6 is transparent and has a heat-resistance against
heat applied to the PET sheet 6 when the PET sheet 6 is subjected to
thermocompression by the heater 7 (see FIG. 4) (in other words, a
heat-resistance against heat of approximately 200° C.). The PET
sheet 6 may be replaced with a polyethylene sheet. Functions of the PET
sheet 6 will be explained later.

[0068]Then, in the step shown in FIG. 4, by the heater 7 used in
thermopress for thermocompression, the EVA sheet 4 is heated up to
approximately 130° C. and fused and at the same time the PET sheet
6 is pressed to the substrate 3 and subjected to thermocompression, so
that laminate-sealing is carried out using ethylene vinyl acetate 4' (see
FIG. 5) and the PET sheet 6.

[0069]Since the EVA sheet 4 is a sheet made of ethylene vinyl acetate that
is a transparent adhesive, when the EVA sheet 4 is subjected to
thermocompression and fused, there is a possibility that the ethylene
vinyl acetate 4' (see FIG. 5) that is a transparent adhesive attaches to
the heater 7. In order to avoid this possibility, the EVA sheet 4 is
coated with the PET sheet 6.

[0070]Since the EVA sheet 4 is coated with the PET sheet 6,
thermocompression is carried out to the PET sheet 6 having no possibility
of being fused by heat of the thermocompression and attaching to the
heater 7. This solves the problem that the ethylene vinyl acetate 4' (see
FIG. 5) attaches to the heater 7 when the EVA sheet 4 is fused.

[0071]In the solar cell module in the step shown in FIG. 4, if an
excessive pressure is applied by the heater 7 to the solar cell module
because of an excessive load of the heater 7 in thermocompression, the
ethylene vinyl acetate 4' (see FIG. 5) spreads over a wide range of the
substrate 3 when the EVA sheet 4 is fused. The ethylene vinyl acetate 4'
thus spread applies a pressure to the bonding wire 1, and this pressure
may cause the wire sweep of the bonding wire 1. However, by sealing and
fixing the bonding wire 1 by the potting resin 5 with high viscosity, the
potting resin 5 prevents the heater 7 from going toward the substrate 3,
preventing the load of the heater 7 from being excessive in the
thermocompression and thus preventing the heater 7 from applying an
excessive pressure. Further, by designing individual potting resins 5 to
have the same height seen from the substrate 3, it is possible to keep
the heater 7 horizontally with respect to the substrate 3, allowing the
solar cell module 150 to have an even thickness.

[0072]The solar cell module having been subjected to laminate-sealing is
the solar cell module 150 shown in FIG. 5 which is a commercial product.
The EVA sheet 4 has been fused and changed into the ethylene vinyl
acetate 4', which fills gaps between the substrate 3 and the PET sheet 6
and serves as an adhesive. The solar cell element 2 and the potting resin
5 sealing the bonding wire 1 are sealed by the ethylene vinyl acetate 4'.

[0073]As described above, the potting resin 5 with high viscosity is epoxy
resin for example. In a case where the solar cell module of the present
invention is applied to an electronic apparatus including a liquid
crystal display, the epoxy resin may be the same as sealing resin used in
a driving device of the liquid crystal display.

[0074]FIG. 6 is a cross sectional drawing showing a configuration of a
solar cell module in accordance with another embodiment of the present
invention.

[0075]A solar cell module 160 shown in FIG. 6 is different from the solar
cell module 150 shown in FIG. 5 in that the solar cell module 160 does
not include the potting resin 5. Further, as shown in FIG. 7, an EVA
sheet 40 made of the ethylene vinyl acetate 4' is different from the EVA
sheet 4 (see FIG. 5) in that the EVA sheet 40 lacks a portion to coat the
bonding wire 1. That is, the EVA sheet 40 is obtained by arranging the
EVA sheet 4 to exclude in advance a portion which exists above the
bonding wire 1 as seen from the substrate 3 when the solar cell element 2
etc. is coated with the EVA sheet 4 (see FIG. 3).

[0076]The EVA sheet 40 is designed to have a thickness larger than the
height of the bonding wire 1 as seen from the substrate 3, i.e., the
height of the bonding wire 1 in a direction perpendicular to a surface of
the substrate 3 closer to the solar cell element 2. Consequently, when
the EVA sheet 40 coats the solar cell element 2 etc., an upper part of
the EVA sheet 40 is positioned above an upper part of the bonding wire 1.
Since the thickness of the EVA sheet 40 is set to range from 0.1 to 1.0
mm according to a standard, there is a case where the thickness cannot be
freely changed. In a case where the thickness of the EVA sheet 40 cannot
be freely changed, the height of the bonding wire 1 as seen from the
substrate 3 should be made smaller so that the thickness of the EVA sheet
40 is larger than the height of the bonding wire 1 as seen from the
substrate 3.

[0077]Since the EVA sheet 40 lacks the portion to coat the bonding wire 1,
there is no load applied to the bonding wire 1 which is derived from the
weight of the EVA sheet 40. Consequently, in the solar cell module 160,
even when the potting resin 5 (see FIG. 1 etc.) is not used, it is
possible to prevent the wire sweep.

[0078]Further, since the potting resin 5 (see FIG. 1 etc.) is not used in
the solar cell module 160, a region which is likely to prevent light from
being incident to the solar cell element 2 is further downsized, allowing
the solar cell element 2 to have further higher efficiency in power
generation.

[0079]It should be noted that in a case where the thickness of the EVA
sheet 40 is smaller than the height of the bonding wire 1 as seen from
the substrate 3, when the EVA sheet 40 coats the solar cell element 2,
the bonding wire 1 protrudes above the EVA sheet 40 as seen from the
substrate 3. When the bonding wire 1 protrudes above the EVA sheet 40,
coating the EVA sheet 40 with the PET sheet 6 may cause the wire sweep of
the bonding wire 1 because of a load applied to the bonding wire 1 which
is derived from the weight of the PET sheet 6. In order to prevent a load
derived from the weight of the PET sheet 6 from being applied to the
bonding wire 1, it is necessary for the EVA sheet 40 to have a thickness
larger than the height of the bonding wire 1 as seen from the substrate
3.

[0080]In order to realize the EVA sheet 40, it is necessary to exclude in
advance a portion of the EVA sheet 4 which portion exists above the
bonding wire 1 as seen from the substrate 3 when the solar cell element 2
etc. is coated with the EVA sheet 4. For this exclusion, it is desirable
to cut out the portion to be excluded, as shown in FIG. 7. Alternatively,
the EVA sheet 40 may be realized by making a concavity (not shown) in the
portion-to-be-excluded of the EVA sheet 4 in order that the EVA sheet 4
does not touch the bonding wire 1 when the solar cell element 2 etc. is
coated with the EVA sheet 4. That is, the EVA sheet 40 should be designed
such that the EVA sheet 40 does not touch the bonding wire 1 when the
solar cell element 2 etc. is coated with the EVA sheet 40.

[0081]As a method for producing the solar cell module in accordance with
another embodiment of the present invention, the following explains steps
of producing the solar cell module 160 (see FIG. 6) with reference to
FIGS. 8-10.

[0082]Initially, as in the step shown in FIG. 2, one end of the bonding
wire 1 is connected with the solar cell element 2 via the surface
electrode 21 and the other end of the bonding wire 1 is connected with an
electrode (not shown) of the substrate 3. Thus, the solar cell element 2
is connected with the substrate 3 by well known wire bonding using the
bonding wire 1.

[0083]In the step shown in FIG. 8, the solar cell element 2 is coated with
the EVA sheet 40. Here, in order that the EVA sheet 40 does not touch the
bonding wire 1 from the above as seen from the substrate 3, the bonding
wire 1 is overlapped with a space obtained by excluding a portion from
the EVA sheet 40 in advance. That is, in the step, the solar cell element
2 is coated with the EVA sheet 40 in such a manner that the bonding wire
1 is not coated with the EVA sheet 40.

[0084]In the step shown in FIG. 9, the EVA sheet 40 is coated with the PET
sheet 6. Since the thickness of the EVA sheet 40 is larger than the
height of the bonding wire 1 as seen from the substrate 3, when the EVA
sheet 40 is coated with the PET sheet 6, the EVA sheet 40 prevents the
PET sheet 6 from going toward the substrate 3. Consequently, the PET
sheet 6 does not touch the bonding wire 1, so that a load derived from
the weight of the PET sheet 6 is not applied to the bonding wire 1.

[0085]In the step shown in FIG. 10, by the heater 7, the EVA sheet 40 is
heated up to approximately 130° C. and fused and at the same time
the PET sheet 6 is pressed to the substrate 3 and subjected to
thermocompression, so that laminate-sealing is carried out using the
ethylene vinyl acetate 4' (see FIG. 6) and the PET sheet 6. Since the EVA
sheet 40 is coated with the PET sheet 6, thermocompression is carried out
to the PET sheet 6 having no possibility of attaching to the heater 7.
This solves the problem that the transparent adhesive attaches to the
heater 7 when the EVA sheet 40 is fused.

[0086]The solar cell module having been subjected to laminate-sealing is
the solar cell module 160 shown in FIG. 6 which is a commercial product.
The EVA sheet 40 has been fused and changed into the ethylene vinyl
acetate 4', which fills gaps between the substrate 3 and the PET sheet 6
and serves as an adhesive. The bonding wire 1 and the solar cell element
2 are sealed by the ethylene vinyl acetate 4'.

[0087]Needless to say, the solar cell module 160 may be further provided
with the potting resin 5 (see FIG. 1 etc.). Further providing the solar
cell module 160 with the potting resin 5 increases the effect of
preventing the wire sweep of the bonding wire 1 and the effect of
protecting the bonding wire 1 in the thermal cycle. However, there is a
possibility that the efficiency in power generation by the solar cell
element 2 drops a little. Therefore, if the effect of protecting the
bonding wire 1 in the thermal cycle is secured as desired without
providing the potting resin 5, it is more favorable to use the solar cell
module 160 shown in FIG. 6 in which the potting resin 5 is not used.

[0088]The heater 7 is preferably a well known heater used for producing a
solar cell module for housing. Since the heater used for producing a
solar cell module for housing has a very broad area capable of
thermocompression, the heater is preferably used in mass production of a
solar cell module, and makes it unnecessary to use other heaters.
Consequently, it is possible to further reduce costs.

[0089]Mass production of the solar cell module of the present invention is
carried out as follows: specifically, a plurality of solar cell elements
are coated with one EVA sheet, and if necessary, the EVA sheet is coated
with a PET sheet. The PET sheet coating the EVA sheet (the EVA sheet in
case of not using the PET sheet) is thermocompressed against a substrate
so that the plurality of solar cell elements are sealed. Then, the
resultant is divided into pieces so that one piece includes one solar
cell element, and thus each piece is regarded as a solar cell module. The
mass production of the solar cell module of the present invention is
carried out in this manner.

[0090]In the solar cell module of the present invention, instead of
sealing the solar cell element with the EVA sheet, the solar cell element
may be sealed by applying a transparent silicon material in a liquid form
to the solar cell element and attaching a glass to the solar cell
element.

[0091]The present invention is not limited to the description of the
embodiments above, but may be altered by a skilled person within the
scope of the claims. An embodiment based on a proper combination of
technical means disclosed in different embodiments is encompassed in the
technical scope of the present invention.

[0092]Specifically, in the solar cell module of the present invention, the
high viscosity resin is preferably designed such that when the
temperature of the high viscosity resin is 25° C., the viscosity
of the high viscosity resin ranges from 5 to 500 Pas. "Pas" indicates
"Pascal second" that is a unit indicative of viscosity in the
International System of Units.

[0093]If the high viscosity resin is designed such that the high viscosity
resin has a viscosity of less than 5 Pas when the temperature thereof is
25° C., the high viscosity resin wets and spreads over the solar
cell element and thus covers the whole of the surface of the solar cell
element which surface is opposite to the substrate. Consequently, light
incident to the solar cell element is blocked by the high viscosity
resin. As a result, in the solar cell module, light energy supplied to
the solar cell element drops greatly, or in a worst case, the solar cell
element cannot receive light energy. Consequently, in the solar cell
element, and therefore in the solar cell module, the efficiency in power
generation drops greatly, or in a worst case, power generation gets
impossible. Further, when the bonding wire is sealed by the high
viscosity resin having a viscosity of less than 5 Pas when the
temperature thereof is 25° C., the bonding wire is fixed less
solidly by the high viscosity resin and the bonding wire cannot have a
sufficient strength against the load, resulting in a possibility of the
wire sweep of the bonding wire when the load is applied to the bonding
wire.

[0094]In contrast thereto, if the high viscosity resin is designed such
that the high viscosity resin has a viscosity of more than 500 Pas when
the temperature thereof is 25° C., the high viscosity resin is
very difficult to flow, which makes insufficient filling of the high
viscosity resin into gaps between the solar cell element and the bonding
wire, and the insufficient filling may cause spaces. This may result in
decrease in the quality and reliability of the solar cell module.

[0095]In view of the above, the high viscosity resin is preferably
designed such that the high viscosity resin has a viscosity ranging from
5 to 500 Pas when the temperature thereof is 25° C.

[0096]The solar cell module of the present invention is obtained by
coating the high viscosity resin and the solar cell element with a first
seat made of a transparent adhesive. In particular, the first sheet is
preferably made of ethylene vinyl acetate.

[0097]Since the first sheet is made of a transparent adhesive, when the
first sheet is subjected to thermocompression and is fused, there is a
possibility that the transparent adhesive constituting the first sheet
attaches to a device for thermocompression (e.g. heater).

[0098]In order to deal with this problem, the solar cell module of the
present invention is obtained by coating the first sheet with a second
sheet that is transparent and has a predetermined heat-resistance.

[0099]The method of the present invention for producing a solar cell
module includes the steps of coating the first sheet with a second sheet
that is transparent and has a predetermined heat-resistance and
thermocompressing the second sheet against the substrate.

[0100]With the arrangement, the first sheet is coated with the transparent
second sheet having a predetermined heat-resistance, specifically, a
heat-resistance against heat applied by the device in the
thermocompression. Consequently, thermocompression is carried out to the
second sheet having no possibility of being fused by heat of the
thermocompression and attaching to the device. This solves the problem
that the transparent adhesive attaches to the device when the first sheet
is fused.

[0101]In the solar cell module of the present invention, the high
viscosity resin is transparent.

[0102]With the arrangement, the high viscosity resin is transparent. This
prevents the high viscosity resin from blocking light incident to the
solar cell element.

[0103]Further, in a case where the first sheet lacks a portion to coat the
wire, coating the first sheet with the second sheet and thermocompressing
the second sheet against the substrate solves the problem that the
transparent adhesive attaches to the device when the first sheet is
fused.

INDUSTRIAL APPLICABILITY

[0104]The present invention provides a solar cell module capable of
preventing the wire sweep. Accordingly, the present invention is
preferably applicable to a solar cell module in which a solar cell
element connected with a substrate by wire bonding is sealed and to
various devices including the solar cell module.